The present invention relates to optical disc drives and, more particularly, to a mechanism and method for securing and covering the optical pickup unit of an optical disc drive when the optical disc drive is not in use.
Optical disc drives are devices that use light to translate information stored on an optical disc to a machine-readable format, e.g., binary data. Examples of optical disc drives are known in the art as compact disc drives (often referred to simply as CDs) and digital versatile disc drives (often referred to simply as DVDs). Some optical disc drives have the additional capability of being able to write data onto an optical disc by the use of a light source, e.g., a laser. Optical disc drives are being used in various applications including music and video playing and recording devices and computer data storage devices. As these applications become more portable, the optical disc drives also need to become more portable. For example, they must be compact and able to withstand the shock and vibration to which portable applications are commonly subject.
The optical disc is a round, flat device similar to a record. Digital data is stored in spiral tracks on the optical disc in much the same way analog audio information is stored in a spiral groove on a record. The data stored on an optical disc, however, is much more compact than the audio information stored on a record. For example, the radial distance between tracks on an optical disc is typically approximately 1.6 microns for a compact disc and less for a digital versatile disc. The data on the optical disc consists of a plurality of optical transitions that are detected or xe2x80x9creadxe2x80x9d by the optical disc drive as the optical disc spins. The optical disc may spin at varying speeds of up to 4000 rpm as data is being read from or written to the optical disc.
A schematic diagram of a side view of a conventional optical disc drive 100 is illustrated in FIG. 1. The optical disc drive 100 is illustrated with an optical disc 110 attached thereto wherein data is stored on an optical surface 112 of the optical disc 110. The optical disc drive 100 has three basic components, a drive motor 120, an optical pickup unit 130, and an optical mechanical assembly 140. The drive motor 120 serves to spin the optical disc 110 at predetermined rates that typically vary from several hundred to several thousand rpm. The optical pickup unit 130 serves to read and write data from and to the optical surface 112 of the optical disc 110. The optical mechanical assembly 140 serves to move the optical pickup unit 130 in a radial direction 152 relative to the optical disc 110 to predetermined locations relative to the optical disc 110.
The optical pickup unit 130 typically has a laser, not shown, to illuminate the optical surface 112, an objective lens 132 to focus the laser, and a photodetector, not shown, to translate light to machine-readable data. Other optical components may be located within the optical pickup unit 130 to direct light between the photodetector and the objective lens 132. Mechanical components may be located in the optical pickup unit 130 and may serve to support the objective lens 132 and to move the objective lens 132 relative to the optical pickup unit 130.
The optical pickup unit 130 emits incident light that is directed through the objective lens 132 and onto the optical surface 112 of the optical disc 110. The optical pickup unit 130 may, as an example, output approximately 20 milliwatts of coherent light having a wavelength of approximately 790 nanometers. Light is reflected from the optical surface 112 of the optical disc 110 through the objective lens 132 and back to the optical pickup unit 130. The light reflected from the optical surface 112 of the optical disc 110 varies in intensity wherein the variations are caused by light reflecting from the optical transitions on the optical surface 112 as the optical disc 110 spins. These variations in intensity are representative of the data stored on the optical surface 112.
As the optical disc 110 spins, the mechanical components in the optical pickup unit 130 move the objective lens 132 in a radial direction 152 and a normal direction 150. Specifically, the optical pickup unit 130 moves the objective lens 132 normal to the optical surface 112 of the optical disc 110 to focus light between the optical surface 112 and the optical pickup unit 130. This focusing allows a sharp image of the optical transitions on the optical surface 112 to be focused onto the photodetector, which improves the operation of the optical disc drive 100. The optical pickup unit 130 moves the objective lens 132 radially relative to the optical surface 112 of the optical disc 110 to follow the tracks on the optical disc 110 as the optical disc 110 spins. This movement of the objective lens 132 is very fine because the objective lens 132 has to follow the tracks with a tolerance of approximately one micron in the radial direction 152 as the optical disc 110 spins. The objective lens 132 is generally mounted to the optical pickup unit 130 by the use of very delicate components. This delicate mounting is required in order for the objective lens 132 to move as precisely as is required to follow the tracks on the spinning optical disc 110 and to focus the optical transitions from the spinning optical disc 110 onto the photodetector.
As described above, the objective lens 132 has to move very precise distances in very short periods in order to follow the tracks on the optical surface 112. This makes the optical pickup unit 130 a relatively delicate device. The fragile nature of the optical pickup unit 130 makes it susceptible to failure due to relatively mild shock or vibration. One cause of failure is due to the objective lens 132 becoming dislodged from the structural components in the optical pickup unit 130 that secure the objective lens 132 to the optical pickup unit. Another cause of failure is due to the components that move the objective lens 132 becoming damaged. These problems are more prevalent in optical disc drives used in portable devices because these optical disc drives are typically subjected to greater and more frequent shock and vibration.
Additional problems occur in optical disc drives that have the objective lens 132 exposed to a user when an optical disc 110 is being exchanged from the motor 120. For example, a user may inadvertently touch the objective lens 132, which may damage the optical pickup unit 130 or contaminate the surface of the objective lens 132 with oils from the user""s skin. In addition, during the exchange of the optical disc 110, the optical pickup unit 130 becomes exposed to the environment and may become damaged if contaminants from the environment enter it. An exposed optical pickup unit 130 may also be dangerous to the user if the optical pickup unit 130 becomes active in the presence of a user. Laser light is typically emitted by the optical pickup unit, which is a relatively bright and narrow beam of coherent light. This light may pose health risks to the user, such as causing irreversible and permanent damage to the user""s retinas.
Therefore, a need exists for a mechanism incorporated into an optical disc drive that will secure the optical pickup unit in a fixed position and out of sight and reach of a user when the optical disc drive is not in use.
One embodiment of the present invention is directed toward the operation for an optical disc drive of the type including a moveably mounted optical pickup unit. The method may comprise providing a cover member attached within the optical disc drive, wherein the cover member is non-movable relative to the optical disc drive. The optical disc drive may be deactivated solely by moving the optical pickup unit to a position adjacent the cover member such that the optical pickup unit is protected by the cover member. The optical disc drive may be activated by moving the optical pickup unit away from the cover member.